Applications of superchargers in internal combustion engines, whereby pressurized air is generated by means of a centrifugal compressor or a positive displacement air pump such as a roots blower, have been in practice for many years. The power to operate the supercharger is obtained from the engine itself, usually by means of a belt and pulley arrangement or direct gear drive.
Supercharging enables the engine to generate more power by means of a higher volume of air being fed to the engine under pressure and corresponding adjustment to fuel flow. It is not uncommon to increase engine power by 50% or higher with the aid of a supercharger, proportional to the pressure of boosted air, which is also proportional to the rotational speed of the supercharger. Therefore, the faster the engine turns, the faster the supercharger speed and therefore higher air pressure and more power is generated.
The drawback of conventional supercharging, however, is the fact that many vehicles need maximum power from start through acceleration, such as from stand still at a traffic light. In such instances, the engine is turning at low or no RPM, which in turn is rotating the supercharger at a low or no RPM, resulting in very low or no air pressure. It is not until the engine speed increases that an appreciable increase in power can be realized.
Although generation of power at high engine speeds is beneficial for high vehicle speeds and heavy load carrying applications, the lack of increased power during acceleration is a serious drawback, particularly in applications with a diesel engine when reduced air flow during acceleration usually results in the emission of black smoke.